This invention relates to a pressing iron, in particular a steam iron, having an electrically heatable soleplate.
As is known, following use for ironing or the like, the soleplate and, where applicable, other parts of pressing irons arranged in close proximity to the soleplate continue to be relatively hot for some time also when the pressing iron is turned off or unplugged from an electrical outlet. In particular shortly after the heating unit is turned off, touching the iron""s soleplate may cause injuries such as burns. There is also the risk that heat-sensitive objects might be damaged or destroyed on contact with a pressing iron that has not yet cooled off sufficiently. Therefore, it is general practice to allow a pressing iron to cool for a while after use before it is packed away in its designated storage place. In doing so, a user has difficulty finding out, without touching the pressing iron, the moment when the iron has cooled down sufficiently to allow safe further handling.
It is an object of the present invention to provide a pressing iron affording particular handling safety.
According to the present invention a pressing iron constructed in particular as a steam iron having a preferably electrically heatable soleplate is equipped with a residual heat warning device configured such as to issue one or several warning signals readily perceptible by a user when the temperature of the soleplate exceeds a threshold temperature. The residual heat warning device, which operates independently of a heating signal, if any, of a thermostat device and is in a position to deliver visual and/or audible warning signals directly perceptible to a user without the intermediary of any further devices, is activated in the presence of temperatures exceeding the threshold temperature, while at temperatures below the threshold temperature being capable of changing over to a condition in which it is either deactivated or, alternatively, issues one or several signals clearly distinguishable from the warning signal. This enables a user to recognize at any time directly when cautious handling is still required.
In a particularly preferred embodiment the residual heat warning device is operable independently of the line voltage so that, for example, an electrical appliance equipped with such a device is in a position to issue warning signals also when the supply of electricity has been turned off or the appliance plug has been pulled. Particularly in electrical appliances in which a pulled appliance plug can be readily seen, the risk involved with the potentially still hot appliance might not be recognized.
The line voltage independent operating capability of a residual heat warning device is particularly useful in pressing irons which conventionally have no power switch, operation being instead started and stopped by plugging and unplugging the appliance cord.
Particularly advantageously, a line voltage independent operation is rendered possible in one embodiment in which the residual heat warning device is electrically operable by providing at least one storage device for the storage of electric energy in order to supply the residual heat warning device with energy. This storage device may be, for example, a primary/secondary battery or a similar storage medium which has been charged independently of the electrical appliance. Preferably the storage device is an integral part of the residual heat warning device and configured such as to be rechargeable when the electrical appliance, in particular the pressing iron, is connected to the line. Thus it can be ensured that on each use of the appliance, also after prolonged periods of non-use, sufficient energy is available for operation of the residual heat warning device.
As storage medium an electrochemically operating secondary battery may be used, for exmaple. In particularly preferred embodiments the storage unit includes at least one capacitor which is preferably a high capacitance capacitor with a capacitance of more than 0.05 farad, in particular between about 0.08 and about 1.2 farad. In contrast to conventional storage by means of secondary batteries, the capacitive storage of electric energy which thereby becomes possible has, among other benefits, the advantage that a capacitor is basically usable without limits regarding the number of its charging cycles, and the stored energy remains essentially constant for the entire service life. In addition, very short charging times can be achieved. Furthermore, capacitors afford low-cost manufacture, and the hardware requirements for the use of charging capacitors may be low, making it possible to keep production costs at an overall economical level.
Where appropriate, the energy required for operation of the warning device may also be stored mechanically as, for example, by means of a spring element or the like, or energy can be generated utilizing the existence of temperature differences in the appliance, as by means of Peltier cells or the like.
Still further, sturdy and low cost embodiments may be contemplated in which the residual heat warning device is operable exclusively by mechanical means. To accomplish this, the residual heat warning device may be provided with at least one mechanical temperature sensor for detecting the temperature of the heat emitting body, meaning the soleplate, needing to be monitored, using for example, a bimetallic element experiencing defined deformations in the range of the threshold temperature. Using the effects of liquid expansion or a thermally induced phase change of a sensor material for temperature detection is also possible. The mechanical temperature sensor may be coupled to a signal device, preferably by mechanical means. This signal device may operate optomechanically, for example, as by using a color element which is movable, using in particular a sliding or swinging motion as in the manner of a flag, in response to temperature and can be observed through a window at temperatures exceeding the threshold temperature, for example. Hybrid arrangements operating, for example, with electric temperature detection and mechanical signal output or vice versa are also possible.
In a preferred embodiment the residual heat warning device has at least one visual signal device which may be provided in addition to a signal device responsible for thermostat settings and which, in a preferred embodiment, is however identical thereto. This signal device may be in particular at least one light emitting diode which, while consuming little energy, delivers in economical manner a warning signal of sufficient luminosity to be readily identifiable also in a dark environment. To enhance the warning effect and lower the energy consumption still further, provision may be made for the visual signal device to be operable intermittently, in particular as a flasher, making it possible to obtain particularly conspicuous warning signals. Where a flashing or pulsating signal or a signal alternating in some other way to indicate residual heat is used, the same signal device can be employed to advantage that is also used for indicating the heating condition of the thermostat by continuous illumination, because these signals are clearly distinguishable from each other. Alternatively or additionally, it is also possible to use, preferably, LEDs differing in color from the colors indicative of the heating condition, or to use electrically operable, audible signal devices.
At least one visual signal device may be arranged on the top side of the pressing iron, in particular on or within the handle. Alternatively or additionally, it is also possible to arrange at least one visual signal device on the bottom side of the pressing iron, for example, in the area immediately adjacent to the soleplate.
Visual signal devices arranged laterally are equally possible. The arrangement of the signal devices is advantageously such that at least one signal device is visible regardless of the position of the pressing iron and the direction from which it is customarily grasped.
It is possible for the residual heat warning device to include at least one temperature sensor for monitoring the temperature of the soleplate serving as heat emitting element, and for the residual heat warning device to be controllable or controlled in dependence upon a temperature signal from the temperature sensor. Elements suited to temperature detection may include, for example, temperature detectors with negative or positive temperature coefficient, thermocouples, suitable temperature sensitive semiconductor elements, infrared detectors, bimetallic elements, metal or fluid expansion elements or temperature sensors responsive to phase changes or the like.
Particularly preferred are embodiments in which the residual heat warning device is configured such as to deliver a warning signal upon the end of heating of the heat emitting element, that is, the soleplate, said signal being present for a predeterminable period of time, preferably independent of the actually prevailing soleplate temperature. Use may be made of the realization that a cooling process follows a substantially predictable and repeatable course, a cooling curve being essentially dependent on such conditions as the thermal capacity of the heat emitting element, the original temperature, the surface properties of the heat emitting element such as size and heat emitting capability, and the ambient temperature. If cooling curves are determined empirically for a given appliance, while taking these parameters into account, it is possible to indicate with relative accuracy a maximum cooling period after which the appliance, proceeding from the maximum operating temperature, will have reached a temperature below a threshold temperature and hence a safe range. Using a suitably connected timer, this cooling period may be utilized for maintaining and subsequently deactivating the warning signal. This enables a residual heat warning device to be provided which does not have a temperature sensing device for detecting the temperature of the heat emitting element. This makes it possible to simplify the design of electrical appliances equipped with such residual heat warning devices and minimize production costs. The storage device is configured/dimensioned in such manner that it will store an amount of energy sufficient for supply to a signal device for the entire period of time until the soleplate has cooled to a temperature below a safe threshold value. For example, an LED will keep flashing for about one hour after the power plug is pulled unless reconnected to the line voltage before this time has elapsed.
Another low-cost possibility of a line voltage independent residual heat warning device may be provided by the residual heat warning device having at least one signal device made of a thermally sensitive material, which is connected with the heat emitting element, that is, the soleplate, in heat conducting manner, being in particular directly affixed thereto, and which experiences a preferably visually perceptible property change, in particular a color change, when the temperature exceeds or drops below the range of the threshold temperature. The signal device may be formed in particular by a coat of temperature sensitive paint applied preferably laterally in the area of the soleplate. It is also possible to provide parts made of temperature sensitive plastics material in the area of the soleplate, the parts"" appearance varying significantly in the range of the threshold temperature, dependently of the temperature.
Pressing irons are known in which at least one condition sensing device for detecting the position and/or the movement of the pressing iron is provided. A corresponding condition signal typically serves the function of turning off the heating unit and/or initiating an alarm signal when the appliance is placed down in a vertical position or when it is in a horizontal position without having been moved for a prolonged period. In such appliances it may be advantageous for the residual heat warning device to be operable in dependence on the condition signal, as will be explained in the following with reference to an embodiment.
In one variant, the residual heat warning device is configured in such manner that in cases where the soleplate, during use, has exceeded a critical temperature threshold lying higher than the threshold temperature, it will also issue a warning signal when the temperature subsequently drops below the threshold value. In such cases, accordingly, the warning signal is independent of the actual soleplate temperature, giving an indication that during the preceding heating cycle a hazardous temperature problem may have occurred as, for example, an excessive deviation towards elevated temperatures. Such a warning signal contributes also to enhancing the handling safety, alerting the user to potentially occurring temperature problems, hence enabling appropriate remedial action to be taken.
These and further features will become apparent not only from the claims but also from the description and the drawing, it being understood that the individual features, whether taken alone or combined in the form of sub-combinations, may be implemented in an embodiment of the present invention and in other fields.